The present invention relates to an optical semiconductor device used, for example, in optical fiber communications.
In the conventional optical semiconductor device, an optical semiconductor light emitting element and a light receiving element for monitoring the emitted light are mounted on a heat sink, and the respective elements are electrically connected to electrode leads supported by the heat sink and hermetically sealed using glass sealant.
In the conventional device as described above, an external package for covering the entire device is usually provided with parallel pins arranged in the vertical direction with respect to the light emitted by the optical semiconductor light emitting element, to facilitate mounting of the device on ordinary substrates, such as a printed wiring board. Therefore, electrode pins projecting from the heat sink are bent in the vertical direction within the external package and connected to external leads of the package.
Recently, high speed operation, miniaturization, and high integration of the electric circuit elements have been increasingly required in optical semiconductor devices used for optical communications. In order to realize the high speed operation, the length of the electrode lead connecting the heat sink and the package must be shortened, and further the inductance of the leads within the package must be reduced.
In a conventional optical semiconductor device, the leads of the heat sink are formed within the package in three dimensions. As a result it has been necessary to mount the device on a printed wiring board by bending the leads. This causes a problem in that the length of the leads becomes excessively large and thereby the inductance of the leads is increased, and higher speed operation of the optical semiconductor device is limited.
In addition, since the pins are bent and then mounted in a package, there exist other problems in that the workability is poor and further a space is inevitably required within the package, thus preventing the miniaturization of the package.
Furthermore, it has been difficult in practice to mount or integrate necessary electric circuit elements on a heat sink or to change the lead wiring arrangement, thereby restricting the freedom of circuit design.